In the prior art bi-directional ratchet spanner has a head and a handle. The head and handle are formed with respective recesses. A braking block is received in the recess of the head and a wing portion of a switch unit is received in the recess of the handle. A lower end of the wing portion is formed with a positioning block. One end of the positioning block is received in a groove of the braking block. By moving the switch unit, the positioning block is driven so as to drive the braking block and thus the direction of the ratchet can be changed.
In the prior art the recess is small and thus the switch unit is also small so that the whole spanner has a strong structure. As a result the user must apply a great force to move the switch unit so that the user's fingers will feel ache.
In another improvement, the head and handle are formed with respective recesses. The head is formed with a via hole for receiving a post-like direction change switch. The switch is formed with a trumpet groove. A thicken driving block can be buckled in the groove so as to change the direction of the braking block and ratchet.
However, above mentioned prior art has the following disadvantages.
The switch unit is thick so as to weaken the structure. Thereby, the groove makes the strength of the head decrease dramatically. Thus, it is not suitable to rotate a rusted screwing element.
Moreover, the post-like direction change switch and the driving block are separated. However, if the manufacturing errors will cause that the operation cannot be performed accurately. Moreover, the trumpet like groove and the recess will make the manufacturing process becomes complicated. Finally, as the above mentioned spanner, the recesses are formed at weak portions of the structure so that the structure is further weakened.